Public address systems for public speaking events are well known. Typically, a person at a podium addresses a crowd through a microphone of a public address system. The voice of the person is detected by the microphone, amplified with an amplifier and the amplified sound is directed to the crowd through one or more speakers.
In more sophisticated systems, the microphone may be a wireless device. In this case, a wireless transmitter may be incorporated into the microphone. A corresponding wireless receiver may receive an audio signal from the transmitter and couple the audio signal to the speakers through the amplifier.
Wireless microphones have a distinct advantage over wired microphones because of the mobility provided. However, wireless microphones typically operate on unlicensed frequency bands that limit the available power and range of such devices.
Because of the flexibility, wireless microphones have become a necessary component in many public proceedings involving many different speakers. In such cases, each wireless microphone is provided with its own transmitter and receiver and each operating on its own frequency under a format known as Frequency Division Multiple Access (FDMA).
While wireless microphones work well, they have a number of features that make them difficult to use in many applications. For example, because of the limited output power, wireless microphones typically operate with a range of less than 100 meters. The limited range is reduced when a speaker places his own body between the wireless microphone transmitter and receiver. In addition, the limited number of frequencies requires that adjacent wireless microphones typically operate on the same or very close frequency ranges, often causing mutual interferences among wireless devices. Because of the importance of wireless microphones, a need exists for better ways of using more wireless microphones in close proximity.